Changes in gene expression serve as a biomarker of exposure for cadmium and copper in the amphipod Hyalella azteca

Presenter: Ryan Gott                                    Status: Graduate Student

Authors: Ryan C. Gott, William O. Lamp, David J. Hawthorne


Abstract: Many useful biomarkers exist for the freshwater amphipod Hyalella azteca Saussure. These consist of changes in life history parameters (survival, reproduction, etc.) and behavior elicited by toxins. Despite the near-model species status of H. azteca, nearly nothing is known about the genetics and molecular biology of this amphipod. To invigorate investigation into molecular biomarkers for H. azteca, its transcriptome was sequenced and assembled. Transcripts of potential biomarker genes were identified and primers were developed for use in RT-qPCR. Exposures of H. azteca to calculated LC10 concentrations of the metals cadmium and copper were conducted. The expression of housekeeping reference genes, such as actin, ubiquitin, and matrix metalloproteinase, was measured for stability and suitability to serve for normalization of the expression of genes of interest (GOI). Expression of GOI, including ferritin, catalase, and superoxide dismutase, was then measured and compared to expression in no-exposure controls. A profile of significantly increased expression across several genes was found to indicate exposure to either metal. Expression of certain unique genes or unique magnitudes of expression served to specify to which metal, cadmium or copper, the amphipod was exposed. In addition to a large set of transcript data derived from the H. azteca transcriptome that will be made publicly available, this work also demonstrates the utility of gene expression as a biomarker of exposure in H. azteca. Future work will include toxins of different classes to demonstrate the versatility of this tool, determination of the limits of detection, investigations of how physical environmental variables like temperature and dissolved oxygen levels could confound the expression signal due to the toxin exposure, and wider-scope comparative transcriptomics.


Urinary Biomarkers of Household Air Pollution: Findings from Nepal

Presenter: Greg Raspanti                             Status: Graduate Student

Authors: Greg A Raspanti MPH, Mia Hashibe PhD, Bhola Siwakoti, Mei Wei MD, Binay Kumar Thakur MD, Chin Bahadur Pun MD,  Yuan-Chin Amy Lee PhD, Amir Sapkota PhD


Abstract: Background: Approximately 50% of the global population relies upon biomass fuels (wood, charcoal, crop residue, dung) for cooking and/or heating purposes.  Household air pollution (HAP) resulting from the use of these solid fuels is of particular concern, given the range of known adverse human health outcomes resulting in an estimated 4 million deaths annually.  While a vast majority of epidemiological studies have relied exclusively on questionnaire as well as environmental monitoring for the quantification of HAP exposure, a more robust exposure assessment method, such as biomarker based approaches are needed to quantify the individual level measure of exposures. Objective:  To evaluate urinary metabolites of 1,3 butadiene as a biomarker of exposure to HAP in Nepal.  Methods: We analyzed urine samples from 606 cytologically/histologically confirmed lung cancer cases and 606 age and gender matched controls collected from B.P. Koirala Memorial Cancer Hospital between 2009 and 2012, using liquid chromatography tandem mass spectrometry (LC-MS/MS) based methods.  The urinary metabolite of 1.3 butadiene (monohydroxybutyl mercapturic acid or MHBMA) was detected in multiple reaction monitoring (MRM) mode and quantified using isotope labeled internal standard (MHBMA-d6).  We used multiple linear regression to quantify the relationship between questionnaire based measure of exposure to HAP and the urinary metabolites of 1,3 butadiene adjusting for known confounders (age, ethnicity, tobacco use, SES status, and geographic residence).  Results/Conclusion:  LC-MS/MS analysis is being currently conducted to quantify the level of MHBMA in urine samples. Our results will show the usefulness of MHBMA as a biomarker of exposure to HAP in large scale studies.  This study is the first of its kind investigating biomarkers of HAP focusing on a population in Nepal.